Light emitting diode (LED) lighting systems are becoming more prevalent as replacements for existing lighting systems. LEDs are an example of solid state lighting (SSL) and have advantages over traditional lighting solutions such as incandescent and fluorescent lighting because they use less energy, are more durable, operate longer, can be combined in red-blue-green arrays that can be controlled to deliver virtually any color light, and contain no lead or mercury.
In many applications, one or more LED dies (or chips) are mounted within an LED package or an LED module, which may make up part of a lighting fixture which includes one or more power supplies to power the LEDs. Some lighting fixtures include multiple LED modules. A module or strip of a fixture includes a packaging material with metal leads (to the LED dies from outside circuits), a protective housing for the LED dies, a heat sink, or a combination of leads, housing and heat sink. An LED fixture may be made with a form factor that allows it to replace a standard threaded incandescent bulb, or any of various types of fluorescent or halogen lamps. LED fixtures and lamps often include some type of optical elements external to the LED modules themselves. Such optical elements may allow for localized mixing of colors, collimate light, and/or provide a controlled beam angle.
Color reproduction can be an important characteristic of any type of artificial lighting, including LED lighting. For lamps, color reproduction is typically measured using the color rendering index (CRI). The CRI is a relative measurement of how the color rendition of an illumination system compares to that of a particular known source of light. In more practical terms, the CRI is a relative measure of the shift in surface color of an object when lit by a particular lamp. The CRI equals 100 if the color coordinates of a set of test surfaces being illuminated by the lamp are the same as the coordinates of the same test surfaces being irradiated by the known source. CRI is a standard for a given type light or light from a specified type of source with a given color temperature. A higher CRI is desirable for any type of replacement lamp.
In some locales, government, non-profit and/or educational entities have established standards for SSL products, and provided incentives such as financial investment, grants, loans, and/or contests in order to encourage development and deployment of SSL products meeting such standards to replace common lighting products currently used. For example, in the United States, the Bright Tomorrow Lighting Competition (L Prize™) has been authorized by the Energy Independence and Security Act of 2007 (EISA). One version of the specification for the L Prize is described in Bright Tomorrow Lighting Competition (L Prize™), Jun. 26, 2009, Document No. 08NT006643, the disclosure of which is hereby incorporated herein by reference. The L Prize is awarded for various categories of lighting products. One recently authorized category of lamp authorized for L Prize consideration is a very high efficiency, bright lamp, for which no particular form factor is required.